Duplex telegraph



(No Model.) 2 SheetsSheet 1.

W. V. MILLER.

DUPLEX TELEGRAPH.

No. 246,181. Patentd Aug. 23,1881.

(No Model.)-

4 2Shets-Sheet2.. W. v. MILLER. Y DUPLEX TELEGRAPH.

Patented Aug. 23,1881.

since.

PATENT WILLIAM V. MILLER, OF PETROLIA, PENNSYLVANIA.

DUPLEX TELEGRAPH.

SPECIFICATION forming part of Letters Patent No. 246,181., dated August 23, 1881,

Application filed June 1, 1881. (No model.)

To all whom it may concern:

Be it known that I, WVILLIAM V. MILLER, a citizen of the United States, and a resident of Petrolia, in the county of Butler and State of Pennsylvania, have invented certain new and useful Improvements in Duplex Telegraphs, of which the following is a specification.

In the transmission of two independent sets of signals over a single telegraph-line simulta neously in opposite directions much interference and inconvenience arise from the false ject of my invention is to avoid the inconveniences thus arising from the effects of the static charge.

To this end my invention consists in a novel organization of apparatus and batteries by means of which the actual amount of the in-' duced or static charge upon the line is lessened and its distribution upon the line effected in such a manner that certain portions of the said charge, being of opposite polarities, are caused to neutralize each other. The portion of the whole charge which tends to pass through the receiving-instrument at the home station is thus greatly diminished, and its effect becomes inconsiderable.

In the accompanying drawings, Figure 1 is a diagram representing my apparatus with the keys at both terminal stations in their normal positions of rest. Fig. 2 shows the same with the key at one station depressed or in action and that of the other station at rest; and Fig. 3 shows the position when the keys at both stations are depressed. Figs. 4 and 5 are diagrams graphically representing the distribution of the static charge under different conditions. I

Referring to Fig. 1, T represents a transmitter, which is actuated by an electro-magnet, t, and a key, K, included in the circuit ofalocal battery, 1, which circuit is indicated by dotted lines. This arrangement is well known and in common use in apparatus of this class. The transmitter T may be actuated directly by the c'finger of the operator, if desired; but the arrangement which I have shown is considered preferable for practical purposes. The electro-magnet which actuates the relay or other receiving-instrument is shown at M, and its helices consist of two independent wires making an equal number of convolutions around the core, and being also substantially equal in their length and in the r resistance. E and c are two main batteries of equal electro-motive force. L is the line, extending from one terminal station to the other, and R is a rheostat or artificial resistance,which is so adjusted as to be equal approximately to one-halfof the linewire L. Upon the lever of the transmitter T is mounted an insulated contactspring, I), which plays between a fixed contact-stop, a, and another similar stop, 0, formed upon the extremity of the lever T, with which it is in permanent electric connection. When the lever T is in its normal position of rest, the key K being open, its extremity rests upon a contact-stop, (I, while at the same time the spring b rests against the stop a, and is thereby.

pressed out of contact with the stop 0. Hence the stops a and d are designated as the resting contacts. If, on the other hand, the key K be depressed, as shown in Fig. 2, the lever T is withdrawn from contact with the stops a and r d, and the spring I) is permitted to come in contact with the stop 0 upon the lever. The latter is therefore termed the working contact. The apparatus at the station at the other end of the line is arranged in the manner precisely similar to that which has been described, and the several parts thereof are designated by corresponding letters of reference, to each of which is affixed the numeral 1, the key being designated as K the transmitter as T and so on. The line-wire L, extending from one station to the other, is connected directly From this transmitter three independent branches diverge, which again unite in a common earth-connection at G. The first branch is connected with the contact-spring b, and includes one coil of the differential receivingmagnet M, as well as one main battery, 0, which latter, having its copper pole presented to the line when in action, may be conveniently designated as the positive battery. The sec- 9 to the axis of the lever of the transmitter T.

0nd branch is connected with the resting contact (I, and includes the remaining coil of the receiving-magnet M and the other main battery, E, which for a corresponding reason may be designated as the negative battery. The third branch is connected with the resting contact a, and includes the artificial resistance R.

It maybe remarked that the operation of the apparatus will be in every respect the same if the points of connection of the ground wire and line-wire are interchanged.

In the three diagrams, which are respectively designed to show the path of the electric current under different conditions or in different positions of the keys. the current proceeding from the positive pole of the battery is designated by arrow-heads placed at intervals upon the line t'lesignating the route of the conductor, and when any line is without arrowheads it is intended to denote that no current passes upon such line. When the keys at both terminal stations are at rest the course of the currents is indicated by the arrow-heads in Fig. 1, as follows: Commencing at the positive pole of the battery IE at the right-hand station, the current passes through one coil of the receiving-magnet M to the stop (1 thence through the lever of the transmitter T and over the line L to the transmitter T at the left-hand station; thence through the stop d and one coil of the receiving-magnet M to the negative pole of the battery E, and from the positir e pole of the said battery to the earth at G, returning by the earth at G of the right-hand station to the negative pole of the battery E A current also traverses the remaining coil of the receiving-magnet M, which current commences at the positive pole of the battery 0, and after passing through the coil goes to the contaet-sprin g l) thence through the resting contact a and artificial resistance R back to the negative pole of the battery 6. A similar current of opposite polarity from the battery 0 traverses the second coil of the receiving-magnet M at the other station. It will appear from an examination of the figure that the two independent coils of each receivinginstrument are traversed by currents of equal stren gth, but opposite polarity or direction, and hence no effect whatever is produced upon their respectii'e armatures. As the artificial resistances It and R are respectively equal to one-half the resistance of the line L, it follows that the strength of the current produced upon the combined batteries E and E through the line L must be precisely equal to that of the battery 0 through resistance It, or of the battery 0 through the resistance R and hence their effect upon the receiving-instrunicnt will be nil, as before stated.

In Fig. 2 the key K at the left-hand station is depressed, the apparatus at the right-hand station being in the same position as before. The line L at the left-hand station is now placed in connection, through contact-spring b, with the positive battery 0. Consequently this battery and the battery E at the other station are placed in the same circuit with their like poles to the line, and as the electromotive forces of the respective batteries are equal, as before explained, no current will traverse the line. At the same time the circuit of the battery E will be interrupted at d, and hence there will be no current in either coil of the receiving'instrument M, which will consequently remain unafiected. The receiving'instrument M however, will respond, for the reason that the current from the battery E in one of its coils is no longer opposed by an opposite line-current in the other coil; hence a signal is produced upon the receiving-instrument M by the depression of the key K.

In Fig. 3 I have shown the position of the apparatus when both keys are depressed. In this case the batteries 0 0 are both included in the main circuit with their unlike poles to the line, and hence the direction of the linecurrent is opposite to that shown in Fig. 1. The circuits of the batteries E and E are re spectively interrupted at the contactstops d and (7 by means of which a signal is given on both receiving-instruments, for the reason that there is no opposing current at either station in the second coil of the receiving electro-magnet.

The improved organization of apparatus and batteries which has been hereinbefore described possesses many important advantages over the system heretofore in general use, and theseare secured without introducing objectionable complications into the apparatus. The

'total amount of battery-power employed is no greater than in the ordinary system,inasmuch as the latter requires at each terminal station a battery sufliciently powerful to actuate the distant receiving-instrument without assist ance, while in my organization two batteries are required at each station, each of which, being assisted by a corresponding battery at the opposite terminal station, requires to be only one-half the electro-motive force ordinarily required. Consequently the total battery-power necessary for a line of given length or resistance is precisely the same as in the ordinary system.

In the distribution ot'thebattery-power which I have adopted very important advantages are realized in practice. In the ordinary system, in which the entire battery required for transmission is situated at the home station, the electrostatic charge of the line is the greatest at the home terminal of the line, and decreases in a uniform ratio to the opposite end of the line, where it becomes zero. \Vhen the discharge takes place at the termination of a transmitted signal three-fourths of the charge finds its way to earth through the coil of the home receiving-instrument, only one-fourth going to earth at the distant end, whereas in my organization, while the total charge of the line is only one-half as great, it is symmetrically distributed, one haltof the line beingposi= tively and the other halt negatively charged, the zero or point of no charge being midway between the terminal stations. This will be more clearly understood by reference to the diagrams Figs. 4 and 5. Referring to Fig. 4, let x 3 be assumed to represent a telegraphline four hundred miles in length, and let the perpendicular w 2 represent the electro-motive force of the battery required to operate such a line according to the ordinary duplex system. The strength of current traversing the line when in connection with the battery will then be represented by the angle a; y 2, while the amount of static charge upon the line and its distribution along its length will be represented by the superficial area of the right-angled triangle x y e. If we consider the line as divided into four sections of one hundred miles each, the static charge accumulated upon each division of the line will be as follows: Sevensixteenths upon the first section, five-sixteenths upon the second, three sixteenths upon the third, and one-sixteenth upon the fourth. If the positive pole of the battery be presented to the line, as in the diagram, the entire charge will be positive. If, now, the line be put to earth at w, the charge of the nearest half of the line will find its way to earth at the home station, and this will amount to twelve-sixteenths or three-fourths of the entire charge of the line, as shown by the diagram. Fig. 5 represents in the same manner the distribution of the charge upon a line where my organization of batteries and apparatus is employed.

00 2 represent the electro-motive force at the homestation,beingonlyone-half whatitwasin the former case. The positive pole of this battery is to the line. y 2 represent the electromotive'force at the opposite terminal station, the negative pole of the battery bein gpresented to the line. In this organization it will be observed that the total electro-motive force is the same as in the first instance, and that thestrength of the current is likewise the same; but the amount and distribution of the static charge are nevertheless materially changed, the zero or point of no charge being situated at a point, 0, midway of the line, instead of at the remote extremity, as before. One-half of the line is now charged positively, as indicated by the triangle .10 0 z, and the other half negatively, as represented by the triangle yo 2, each of these being equal in area to foursixteenths, orone-fourth of the triangle .1; y z in Fig. 4. Consequently the total charge upon the whole line when the circuit is closed is only one-halt as much as in the first instance. Now, if the line be put to earth at w, the positive charge of the first one hundred miles only escapes to earth at that point. The positive charge of the second hundred miles unites with and neutralizes the negativecharge of the third hundred miles, while the negative charge ofthe fourth hundred miles goes to earth at the distant station. From these considerations it follows that with a given length of line and a given strength of working current the total amount of static electricity which is discharged to earth through the home receiving-instrument can in any event be only one-fourth as much as in the ordinary duplex system. Hence its effect upon the instrument or lines of ordinary length becomes wholly inappreciable, while even on lines of very great length it is so small that it may be counteracted without difficulty by proper adjustment ot' the instruments.

I have in some instances made use of a modification of the organization hereinbefore described, which consists in placing the main batteries E and E (these being in effect two sections of a single battery) at some point on the main line L, preferably about midway be tween the two terminal stations, and of course dispensing with them in the branch circuits at the terminal stations, as shown in the drawings. In thiscase it may be necessary to insert an artificial resistance ofmoderate amount, technically termed a spark-coil, in each of the branches from which the batteries E and E have been removed. The principle of operation remains the same as in the first instance, and need not, therefore, be more particularly described.

I claim as my invention- 1. The combination, substantially as hereinbefore set forth, of a main line, the lever of a transmitter connected therewith, one workin g contact and two resting contacts for said transmitter, and three branch lines, connected respectively to the said three contacts and uniting in a common earth-terminal.

2. The combination, substantially as here inbefore set forth, with the lever of a key or transmitter, of a contact-spring attached to said lever, but insulated therefrom, a resting contact for said spring, which is insulated from the lever, a working contact for said spring, which is electrically connected with the lever, and an independent resting contact for the lever,which is insulated from said contact spring.

3. The combination, substantially as hereinbefore set forth, of a main battery, a main line, a branch line containing an artificial resistance, and a transmitter for forming an electrical connection between the battery and said main and branch lines in alternation.

4. The combination, substantially as hereinbefore set forth, of a key, a main line, two branch lines, in which are respectively included a main battery and a rheostat, a receiving-instrument provided with two independent magnetizing-helices, one of which is included in the same branchwith the main battery, and a transmitter actuated by said key, for connecting said battery with the main line when the key is closed and with-the rheostat when the key is open.

5. The combination, substantially as hereinbefore set forth, of a key, a main line, three branches, in which are respectively included a IIO positive battery, a negative battery, and a In testimony whereof I have hereunto subrhcostat, a receiving-instrument provided with scribed my name this 30th day of May, A. D. two independent magnetizing-helices respect- 1881.

ively included in a branch with one of said WILLIAM V. MILLER. 5 batteries, and a transmitter actuated by said Witnesses:

key, for connecting the main line alternately F. F. HERB,

' to each of said battery branches. l ORLANDO l WOOD. 

